Recuperative heat exchanger for gas turbines



April 21, 1970 R. WISOKA Q 3,507,115

RECUPERATIVE HEAT EXCHANGER FOR GAS TURBINES Filed July 28 1 s? 4 Sheets-Sheet 1 I i I INVENTOR Leon R. Was/k0 BY/M #W ATTORNEYS 3,507,115 RECUPERATIVE HEAT EXCHANGEB FOR (ms TURBINES- Filed July 28 1967 Afifil 21, 1970 I 1.. R WISOKA 4 Sheets-Sheet 5 ATTORNEYS April 21, .1970

R. WISOKA RECUPERATIVE HEAT EXCHANGER FOR GAS TURBINES 4 Sheets-Sheet 4.

Filed July 28, 1967 INVENTOR Lepn R. Was/Ira Bw wymwyww ATTORNEYS United States Patent US. Cl. 6039.51 7 Claims ABSTRACT OF THE DISCLOSURE A heat exchanger for recovering heat from the hot exhaust gases of a gas turbine and imparting such recovered heat to the incoming air on its way to the combustion chambers of the turbine. The exchanger surrounds the turbine and combustion chambers, the latter being arranged annularly about the turbine, and provides a countor-flow of hot combustion products and fresh air from the compressor. Built in radially and axially directed turning vanes within the exchanger provide an even distribution of cold air entering and discharging from the exchanger with a minimum of headering ducts.

BACKGROUND OF THE INVENTION The invention relates generally to counter-flow heat exchangers wherein hot gases flowing in one direction between a pair of spaced metallic walls transfer their heat through said walls to cooler gases flowing in the other direction on the other side of the spaced walls. Corrugated metallic separators or cores between the spaced walls, with their corrugations parallel to the direction of flow of the hot and cold gases, are welded and brazed to the spaced walls so there is a metal to metal contact therebetween to more efiectively transfer heat from the separators to the walls. The corrugated separators or cores serve to bring more metal surface into contact with both the hot and the colder gases to better absorb heat from the hot gases and transfer it to the cold gases. Heat exchangers of this type are generally rather difficult to assemble and manufacture because of the multiplicity of parts and complexity of headers or duct work necessary for the even distribution of hot combustion gases or the colder incoming air to the corrugated separators. Prior art is exemplified by the Patent 3,255,818 to Beam et a1. and 3,285,326 to Wosika.

SUMMARY OF THE INVENTION The exchanger of the instant invention is of simplified construction and includes a convoluted separator sheet which may be of indefinite length, being wound over and around several or all of the corrugated sheets or cores. The separator sheets and corrugated sheets are of involute form so that the distance between the separator sheets and the depths of the corrugated sheets are uniform from the inner diameter of the exchanger of its outer diameter. Air side turning vanes at the inlet and outlet ends of the cold air corrugated metal cores are similarly of involute shape, and eliminate complicated headering constructions.

In heat exchangers of the type to which the invention pertains it is desirable that they be as compact as is reasonably possible, that the power utilized in forcing the air and gases through the exchanger be as low as possible, and that the rate of heat transfer between hot and cold gases be high so that the cost of the exchanger is more than fully warranted by its efiiciency. Since the heat from the hot combustion products is first transmitted to metallic walls and from them to the colder incoming air, the efiiciency of the exchanger is increased by the surface 3,507,115 Patented Apr. 21,1970

area of metal exposed to the gases and air. Leakage of hot combustion gases into the incoming fresh air and vice versa must be prevented.

In order to increase the area of metal exposed to the hot gases or cold air, corrugated metallic sheets, which may be termed air cores or gas cores, arranged alternately within hot and cold air passageways, are separated by metallic separator sheets through which the heat transfer from the hot combustion gases to the cold entering air is effected by reason of metallic bonding such as brazing of the corrugated sheets to the separator sheets. The corrugated metal of the air cores, of the combustion gas cores and the separator sheet between them is relatively thin and thus readily formed, being preferably in the order of four thousandths (0.004) of an inch thick. stiffening spacer bars between the edges of the separator sheet on opposite sides of a corrugated core serve to seal the edges of the separator sheet as well as to stiffen both the cores and the separator sheets.

Cold air from the compressor is fed radially into turning vanes within the exchanger, which redirect it in an axial direction in counter-flow to hot exhaust gases. At the other end of the exchanger the air passes through another set of turning vanes that direct it radially inwardly, after which the heated air flows directly to the combustion chambers of the burners.

It is accordingly a primary object of the invention to provide an improved recuperative heat exchanger of simplified construction for gas turbines.

It is another important object of the invention to provide a novel heat exchanger of small overall size and high efiiciency.

Still another important object of the invention is the provision of a novel heat exchanger having uniform flow by means of novel air side turning vanes leading to and from the air inlet and outlet, which turning vanes are in full heat exchange relationship with the cores for the hot combustion gases discharging from the turbine.

Another important object of the invention is the separation of the cold air cores from the hot combustion gas cores by means of a continuous convoluted separator sheet that is wound over and under these cores and is sealed at its edges and reinforced by spacer bars having involute shapes corresponding to the desired curvature of the cores and the separator sheets.

Additional objects will become apparent from the appended claims and from the following description and the drawings, wherein:

FIGURE 1 is a view in side elevation, partly in section through the combustion gas core along line 1-1 of FIG- URE 2, of a gas turbine utilizing an embodiment of a recuperator in accordance with the invention.

FIGURE 2 is a perspective view of a portion of a recuperator alone, before assembly with a turbine.

FIGURE 3 is a longitudinal section through one of the air cores of the recuperator taken along line 3-3 of FIG- URE 2.

FIGURE 4 is an enlarged transverse sectional view taken substantially along the line 44 of FIGURE 3, but showing the elements greatly exaggerated in thickness.

FIGURE 4A is a sectional view of a portion of the recuperator along the line 4A-4A of FIGURE 3.

FIGURE 4B is an enlarged fragmentary elevation of the outlet end of the air passages looking in the direction of arrows 4B4B of FIGURE 3.

FIGURE 5 is an end view of a portion of the cold side of the recuperator.

FIGURE 6 is a view in enlarged section substantially along the line 6-6 of FIGURE 5.

FIGURE 7 is a view in enlarged section substantially along line 77 of FIGURE 5.

FIGURE 8 is a view in enlarged section substantially along the line 66 of FIGURE but at the other end of the recuperator and looking in the other direction.

FIGURE 9 is a top plan View of a portion of a modification of an element of the assembly.

FIGURE 10 is a sectional view similar to that of the lower right end of FIGURE 3, but using the modification of FIGURE 9.

Referring now more particularly to the drawings, FIG- URE 1 shows a gas turbine of conventional construction in which environment the recuperator of the present invention is expected to have its greatest utility. The entire turbine, including the surrounding recuperator is of generally cylindrical configuration about a centerline 10, and is indicated by the reference number 11.

Atmospheric air enters an axial inlet 12 and then a compressor 13, from which it exits through an annular series of outwardly radially directed ports 14 to an annular plenum chamber 15. The air in the plenum chamber is raised by the compressor 13 to a pressure of approximately 40 pounds per square inch and a temperature of substantially 400 F. This air now passes radially outwardly into the recuperator indicated generally at 16 and thence to the right and radially inwardly to an annular chamber 17 in which are disposed an annular series of burner nozzles 19 positioned in combustion chamber 18 into which the air from chamber 17 enters through peripheral openings 20. Initial ignition is provided by a spark plug or the like 21. Chambers and 17 are separated by a common wall 9. The hot combustion products then enter nozzles 22 and pass through turbine blades 23 which drive a power output shaft (not shown) through a gear train, some of which is mounted in a housing 24. The power output shaft also drives the compressor 13. The hot combustion gases leaving the turbine fiow into an annular exhaust gas manifold 25 and into the right end of the recuperator 16, thence to the left and into an annular discharge gas manifold scroll 26 to a discharge gas outlet 27.

Referring to FIGURES 2, 3 and 4, the recuperator comprises a hollow cylindrical inner shell 28 and a concentric outer shell 29, separated by a series of corrugated air cores 30 and combustion gas cores 31, there being a continuous reversely folded separator sheet 32 extending be- .tween the cores 30 and 31, as shown in FIGURE 4 and extending the length of the corrugated hot gas core 31. As best seen in FIGURE 3, the inner shell 28 terminates at the outer edges of reinforcing rings 37 and 38 which are welded to the inner surface of the inner shell 28 to provide bases for welding bellows members or the like for assembly with the gas turbine. Similar outer reinforcing rings 39 and 40 may be Welded to its outer surface.

Spaced from the ends of inner shell 28 are a pair of end liners 45 and 46. These end liners are of the same diameter and thickness as the inner shell 28, are in axial alignment therewith, and in effect form a portion of or extensions of the inner shell when the recuperator is completely assembled.

The corrugated hot gas cores 31 do not appear in FIG- URE 3, but they extend the entire length of the outer shell 29 of the recuperator, while the corrugated air cores 30 extend only to the ends of inner shell 28.

The separator sheet 32 and the hot gas cores 31 bridge the spaces between the end of inner shell 28 and end liners 45 and 46 to which the sheet 32 is spot or tack welded. In alignment with each of the corrugated air cores 30, and at the opposite ends thereof are side turning vanes 41 and 42 having corrugations 43 and 44 therein of the same depth as the corrugations in the air core 30 so that the total thickness of the turning vanes is the same as that of the air core 30 and will engage the same walls of the separator sheet 32.

As shown in FIGURE 3 the corrugations 43 of the side turning vanes 41 are curved so that the compressed air flowing radially outwardly between the separator sheets 32 and into the side turning vane 41 has its direction changed by degrees to flow in an axial direction through the corrugated air core 30. They also serve to divide the incoming air and channel it so that it is fed substantially equally to the air core. At the other end of the recuperator the corrugations 44 in the side turning vane 42 serve to redirect the axially flowing air to an inward radial path to the hot air outlet. The air flowing through the side tuming vanesf41 and 42 is, of course, in full heat exchange relationship, through the separator sheet 32, with the hot combustion gases in the corrugated gas cores 31.

The separator sheet 32 extends around the corrugated air cores 30 and gas cores 31 as shown in FIGURE 4, extending the full length of the outer shell 29, thus also passing over and around the side turning vanes 41 and 42. FIGURE 4A shows how the inner ends of the separator sheet divides the entering air so that it enters the inner ends of the side turning vanes 41. The metal forming the cores 30 and 31, side turning vanes 41 and 42 and separator sheet 32 are shown in greatly enlarged thickness in FIGURES 3 and 4 for illustration only. Actually the metal of these elements is quite thin, being substantially only about four one thousandths (.004) of an inch thick, and they are thus flexible and easily formed.

The separator sheet 32 could be a continuous sheet around all of the cores and side turning vanes and having its ends overlapped and joined. However, for ease of assembly it is preferable to use several lengths of separator sheet, with each length being wrapped around a group of cores and then joined as by welding to the next length as indicated by the joints 48 and 49 in FIGURE 4.

The entire assembly of cores, separator sheet and side turning vanes do not extend directly radially between the inner shell 28 and the outer shell 29 but are curved lnto a involute shape as shown in FIGURES 2, 4 and 5. This permits the corrugations in the metal of the air and gas cores 30 and 31 to be of equal depth and the spacing between the adjacent walls of the separator sheet to be equal between the inner and outer shells 28 and 29. The cores 30 and 31 are thus more easily formed and the cost of this entire assembly is reduced, besides providing better heat exchange between hot exhaust gases and incoming air.

At the ends of the recuperator, means are provided to close the spaces between adjacent edges of the separator sheet 32 on the two sides of each air side turning vane 41 and 42. At one end of the recuperator, preferably the end where the hot exhaust gas enters, these closures take the form of spacer bars 50 shown in FIG- URE 8. They are generally rectangular in cross-section, but the sides may 'be slightly rounded as shown. They fit snugly between the walls of adjacent ends of the separator sheet 32 in alignment with the air cores 30 and the side turning vanes 42, extending from the inner shell 28 to the outer shell 29, have the same involute curvature from end to end as the cores, and are spot or tack welded in place to the aforesaid elements, serving to stiffen the recuperator and hold it together after removed from the jig or fixture which holds it during assembly. The entire recuperator is brazed in a suitable facility as the last operation in its construction, thus sealing all gaps which would otherwise permit mixing of incoming air with exhaust gases.

For a short distance from the shell 20, corresponding to the height of the gussets 34 as shown in FIGURE 3, the outer surfaces of the spacer bars 50 are grooved as shown in FIGURE 8 to seat the short legs of the gussets 34, which are spot or tack welded thereto, the long legs of the gussets being appropriately secured, as by welding, to the outer surface of the end liner 46. These gussets serve to strengthen the assembly, and are curved to the same curvature as the spacer bars 50.

The closures at the other end of the separator sheet 31 may be as described above, although an alternate construction is shown in FIGURES 5, 6 and 7. 'In this case the spacer bars 51 are not much longer than the short legs of the gussets 34, and are grooved on their outer surfaces to receive the gussets. Beyond the outer ends of the spacer bars the end portions of the separator sheet are pinched and resistance welded together as shown in FIG- URE 7. This construction is less costly than that of FIG- URE 8 but that shown in FIGURE 8 gives better support to the assembly during the final brazing step. 1f the construction of FIGURE 8 is used at only one end it is preferably used at the end that the hot exhaust gases enter the gas cores 31, this being at the left end in FIG- URE 3. The gussets 34 at this end have the same curvature as the spacer bars 51.

While the temperatures of the inlet and outlet air will depend upon several factors such as the temperature of the hot exhaust gases from the turbine and the dimensions of the recuperator the following table illustrates the results obtainable from a recuperator such as shown in FIGURE 2 wherein the recuperator is 24 inches long, the diameter of the inner shell is approximately 29.5 inches and the diameter of the outer shell is approximately 42.8 inches.

Air inlet at 40 lbs./ sq. in. and 400 F. Air outlet temperature is 1100" F. 'Exhaust gas inlet temperature is 1200 F. Exhaust gas outlet temperature is 500 F.

To accommodate the expansion of the air the vanes 42 are about 20 percent wider than the vanes 41.

FIGURES 9 and 10 illustrate another embodiment of an element of the assembly. FIGURE 10 shows in section the inner fold of a separator sheet 32 but does not show the side turning vanes 41, In this embodiment the end liner 55 is of larger diameter than the inner shell 28, with which it is coaxial. The diameter of the end liner 55 is such that teeth 56 (FIG. 9), formed by serrating the inner end of the liner, may be inserted into the folds of the separator sheet 32 at their inner ends where they are folded around the gas cores 31.

Preferably there is a tooth 56 for each fold in the separator sheet 32. After insertion of the teeth they are spot or tack welded to the separator 32. While some deformation of the edges of the gas cores 31 may occur when the teeth 56 are inserted into the folds of the separator sheet, such deformation will be minimal since the thickness of the end liner 55 is only 0.035 inch and the teeth 56 are not very long. After the folds of the separator sheet 32 have been welded to the teeth 56 a reinforcing ring 57 may be spot or tack welded to the folds of the separator sheet 32.

The toothed end liner at the other end of the recuperator is not shown since the construction at the other end is the same as shown in FIGURE 10. The two toothed end liners form in effect portions or extensions of the inner shell 28 when the recuperator is assembled.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the forego ng description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

What is claimed and desired to be secured by Letters Patent is:

1. A recuperator for a gas turbine having an air compressor, a first annular plenum chamber receiving the compressed air, a second annular chamber housing a combustion chamber, a turbine, an annular exhaust gas manifold receiving combustion gases from the turbine and an annular discharge gas scroll, the recuperator being annular and located between said exhaust gas manifold and said exhaust gas scroll and surrounding said first and second annular chambers, said recuperator comprising: spaced concentric cylindrical inner and outer shells; said outer shell extending substantially from the exhaust gas manifold to the discharge gas scroll; exhaust gas cores extending substantially the length of said outer shell; air cores between each pair of adjacent gas cores but terminating at each end a substantial distance from the ends of said gas cores; a separator sheet between each air core and gas core and extending the length of said gas cores; first and second air turning vanes at each end of said air cores, in alignment with said air cores and between said separator sheets, said air turning vanes extending substantially from the ends of said air cores to the ends of said gas cores, said first air turning vanes at one end of said air cores including means to admit air radially outwardly and then turn it to flow axially through said air cores to said second air turning vanes at the other ends of said air cores, said second air turning vanes including means to redirect the axially flowing air to flow radially inwardly; said inner shell being provided with openings to admit air from the first annular plenum chamber of the turbine to said first air turning vanes and to discharge air from said second air turning vanes to the second annular chamber of the turbine, said air cores, air turning vanes and exhaust gas cores having corrugations therein to divide the flow of air or gas flowing between said separator sheets, all of said corrugations being of substantially equal depth, and the spacing between adacent separator sheet portions being substantially equal from said inner shell to said outer shell.

2. A heat recuperator comprising: a pair of spaced concentric inner and outer shells; means forming exhaust gas cores extending substantially the length of said outer shell, and from said inner shell to said outer shell; said inner shell being provided with a first opening therethrough adacent a first end thereof to provide an air entrance and a second opening therethrough adjacent the second end thereof to provide an air discharge; means forming inlet air turning vanes extending substantially from said inner shell to said outer shell and in alignment with said air entrance in said inner shell, said inlet air turning vanes havmg means to direct radially outwardly flowing air from said air entrance in said inner shell to a longitudinal path between said inner and outer shells; means forming discharge an turning vanes extending substantially from said 1nner shell to said outer shell and in alignment with said a r discharge opening in said inner shell, said discharge air turmng vanes having means to direct longitudinally flowing air inwardly toward said air discharge opening in said inner shell; means forming air cores extending longitudinally between said inlet air turning vanes and said discharge air turning vanes and in longitudinal alignment therewith between said inner and outer shells; said exhaust gas cores being arranged between adjacent sets of said aligned air inlet turning vanes, discharge air turnmg vanes and air cores; separator sheet means between each gas core and adjacent set of aligned air inlet turning vane, discharge air turning vane and air core, to prevent the mixing of air and exhaust gases in adjacent air and exhaust gas passageways, said air cores, air turning vanes and exhaust gas cores having corrugations therein to divide the flow of air or gas flowing between said separator sheet means, all of said corrugations being of substantially equal depth, and the spacing between adjacent separator sheet portions being substantially equal from said inner shell to said outer shell.

3. In the device described in claim 2, said separator sheet means comprising: a continuous sheet passing around the inner ends of the gas cores adjacent said inner shell, thence between the gas cores and adjacent aligned air cores and air turning vanes, and thence around the outer ends of the aligned air cores and air turning vanes adjacent said outer shell.

4. In the device described in claim 2, said separator sheet means comprising more than one sheet, each sheet being wrapped over and between several gas cores, air cores and aligned air turning vanes of a group, the end of the one sheet being secured to the end of the next separator sheet.

5. In the device described in claim 2, closures for'the outer ends of said air turning vanes adjacent the outer ends of said gas cores, said closure being in the form of reinforcing bars secured to the end portions of said separator sheet means adjacent their outer ends and in alignment with said air turning vanes.

6. In the device described in claim 5, said air cores, air turning vanes, gas cores and reinforcing bars all being shaped in an involute form between said inner and outer shell.

7. An annular heat recuperator comprising, means forming inner and outer tubular wall structures, a'plurality of first cores extending from end to end of said recuperator and across the radial width of said recuperator and providing axially extending passages from end to end of said recuperator, a plurality of second cores extending across the radial width of said recuperator also providing axially extending passages, said first and second cores be- 20 ing arranged alternately around said recuperator and said first cores extending beyond the ends of said second cores, guide vane assemblies at the opposite ends of said second cores and interposed between the projecting ends of said first coresfor guiding fluid between the inner periphery of said recuperator and said first cores, said first and second cores-and said guide vanes extending between said inner and outer .wall structures along an involute curve and means for isolating said first cores from said second cores and the associated guide vanes.

References Cited UNITED STATES PATENTS FREDERICK L.MATTESON, JR., Primary Examiner R. A. DUA, Assistant Examiner US. Cl. X.R. 165--l66 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 591 5 Dated Anril 21 1910 Inventor(s) 1g.- I u- 1k 3 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

The inventor-s name is consistently misspelled. It should be "wosika Column 1. line 58, "of" (second occurrence) should be --to--.

Attesl:

mm 1:. sum. 3- Aflesling Officer Commissioner of Patents FORM P0-1050(10-69) us c 50 5 259 7 t u.s, sovimmiuv rnmtme OFFICE: In O-Sii-JJ 

